CN102334292A - Voltage-frequency conversion circuit and blood pressure measurement apparatus provided with same - Google Patents

Abstract

A resistor (16) is provided between an input terminal and a node (N0). A switch (15) is provided between the node (N0) and a ground voltage (GND) and closes according to the voltage level of the node (NC). A resistor (13) is provided between the nodes (N0, NA). A resistor (12) is provided between the node (NA) and one side of the input node of an NOR circuit (11A). A capacitor (14) is connected between the nodes (NA, NC). The input node of the NOR circuit (11A) is connected through the resistor (12) between the node (NA) and the ground voltage (GND). The input node of the NOR circuit (11B) is connected to the output node of the NOR circuit (11A) and to the ground voltage (GND). The input node of the NOR circuit (11C) is connected to the node (NC) and the ground voltage (GND).

Description

Voltage/frequency change-over circuit and blood pressure measurement apparatus with this circuit

Technical field

The present invention relates to the voltage/frequency change-over circuit, relate to the RC oscillating circuit especially.

Background technology

In the past, when analog quantitys such as instrumentation voltage, electric current and electrostatic capacitance, utilized the method (A/D conversion) that the analogue value is converted to digital value.This mode has integral form, variety of ways such as type, delta sigma-type relatively successively, and selects as the best conversion regime of the analog quantity of object.In addition, by each company the IC (integrated circuit) of integrated these circuit has been realized commercialization.

Yet the cost of these IC is higher, in addition, must use software control.

And, if carry out high-precision instrumentation and improve accuracy, then have the problem that increases corresponding cost.

Aspect practical, what can realize the most reliable and high-precision mensuration is frequency, as long as utilize frequency, just can reduce cost and realizes high-precision A/D conversion.

For example, in japanese kokai publication hei 9-113310 communique, disclose piezoresistance formula sensor device, disclose the mode that converts frequency when the deviation of transducer revised to.

In addition, in japanese kokai publication hei 10-104292 communique, disclose the static capacity type sensor device, in the document, disclose the circuit that will convert frequency to according to the capacitive component that pressure changes.

The prior art document

Patent documentation

Patent documentation 1: japanese kokai publication hei 9-113310 communique

Patent documentation 2: japanese kokai publication hei 10-104292 communique

Summary of the invention

The problem that invention will solve

Yet; In the piezoresistance type sensor device that japanese kokai publication hei 9-113310 communique is put down in writing; The mode of utilizing the CR oscillating circuit is disclosed; But adopted calculate the frequency of oscillation that two CR oscillating circuits are vibrated cycle time difference the complex conversion mode, and have the high problem of cost.In addition, in the static capacity type sensor device that above-mentioned japanese kokai publication hei 10-104292 communique is put down in writing, have the influence and the also high problem of cost that receive temperature characterisitic easily.

The means that are used to deal with problems

The objective of the invention is to, provide with easy mode and realize high-precision voltage/frequency change-over circuit and blood pressure measurement apparatus with this voltage/frequency change-over circuit.

The voltage/frequency change-over circuit of one aspect of the present invention has the RC oscillating circuit that comprises capacitive component and resistance components.The RC oscillating circuit comprises: input terminal, and it is used to receive input voltage, first resistive element; It is connected between the input terminal and first internal node, first capacitor, and one electrode is connected with first internal node; Its another electrode is connected with second internal node, second resistive element, and itself and first capacitor are in parallel; And an one of which Lead-through terminal is connected with first internal node, first logical circuit, and it is connected with another Lead-through terminal of second resistive element; And be connected between first internal node and second internal node via second resistive element, second logical circuit, it is connected with second internal node; Be used to export oscillator signal in response to the output signal of first logical circuit, first switch element, it is according to the voltage level of second internal node; First internal node and the fixed voltage that are connected with an electrode are electrically connected, so that first capacitor carries out charge/discharge.

Preferably, input voltage is equivalent to the output voltage of piezoresistance formula transducer.

Preferably, first switch element is threshold value conducting when above at the voltage level of second internal node, so that first internal node and the fixed voltage that are connected with an electrode be electrically connected, thereby first capacitor is discharged.First switch element is in the not conducting during less than threshold value of the voltage level of second internal node, so that first internal node that is connected with an electrode is connected with input voltage, thereby first capacitor charged.

Preferably, this voltage/frequency change-over circuit comprises: the 3rd resistive element, and it is connected between input terminal and the 3rd internal node; Second capacitor; One electrode is connected with the 3rd internal node, and another electrode is connected with the 4th internal node, the 4th resistive element; Itself and second capacitor are in parallel, and an one of which Lead-through terminal is connected with the 3rd internal node.First logical circuit has: first phase inverter; It is connected with another Lead-through terminal of second resistive element; Exclusive-OR circuit, its receive first phase inverter lead-out terminal and the 4th resistive element another Lead-through terminal input signal and export second internal node to.Second logical circuit has: second phase inverter, and it is connected between second internal node and the 4th internal node, the 3rd phase inverter, it is connected with the 4th internal node.This voltage/frequency change-over circuit also comprises the second switch element, and this second switch element is electrically connected the 3rd internal node and the fixed voltage that are connected with an electrode, thereby second capacitor is discharged according to the voltage level of the 4th internal node.

The blood pressure measurement apparatus of one aspect of the invention has: cuff, and it is used to be wound on the location of determined person's regulation, pressure sensing cell, it detects the pressure in the cuff.Pressure sensing cell comprises: piezoresistance formula transducer, its be used to produce with cuff in the corresponding voltage of pressure, the RC oscillating circuit, it comprises capacitive component and resistance components.The RC oscillating circuit comprises: input terminal, and it is used to receive input voltage, first resistive element; It is connected between the input terminal and first internal node, first capacitor, and one electrode is connected with first internal node; Its another electrode is connected with second internal node, second resistive element, and itself and first capacitor are in parallel; And an one of which Lead-through terminal is connected with first internal node, first logical circuit, and it is connected with another Lead-through terminal of second resistive element; And be connected between first internal node and second internal node via second resistive element, second logical circuit, it is connected with second internal node; Be used to export oscillator signal in response to the output signal of first logical circuit, first switch element, it is according to the voltage level of second internal node; First internal node and the fixed voltage that are connected with an electrode are electrically connected, so that first capacitor carries out charge/discharge.

The invention effect

Voltage/frequency change-over circuit of the present invention and blood pressure measurement apparatus make first switch element carry out charge or discharge to first capacitor according to the output signal of first logical circuit.The charging interval of first capacitor changes according to the input voltage that input terminal received, and therefore can adjust the frequency of oscillator signal with easy mode.

Description of drawings

Fig. 1 is the stereoscopic figure of the sphygmomanometer 1 of embodiment of the present invention.

Fig. 2 is the block diagram of hardware configuration of the sphygmomanometer 1 of expression embodiment of the present invention.

Fig. 3 is the figure of pressure sensor 32 that is used to explain the piezoresistance formula of embodiment of the present invention.

Fig. 4 is the figure that is used to explain existing RC oscillating circuit.

Fig. 5 is the figure of voltage level that is used to explain each node of existing RC oscillating circuit.

Fig. 6 is the figure that is used to explain the voltage/frequency change-over circuit 34 of embodiment of the present invention.

Fig. 7 is the figure of voltage level of each node that is used to explain the voltage/frequency change-over circuit 34 of embodiment of the present invention.

Fig. 8 is the figure of voltage/frequency change-over circuit 34# that is used to explain the variation of embodiment of the present invention.

Fig. 9 is the figure of voltage level of each node of voltage/frequency change-over circuit 34# that is used to explain the variation of embodiment of the present invention.

Embodiment

With reference to accompanying drawing, execution mode of the present invention is carried out detailed explanation.In addition, to the identical Reference numeral of part mark identical among the figure or that be equal to, do not repeat its explanation.

< about outward appearance and structure >

At first, outward appearance and the structure to the blood pressure measurement apparatus (to call " sphygmomanometer " in the following text) 1 of embodiment of the present invention describes.

(about outward appearance)

Utilize Fig. 1, the sphygmomanometer 1 of embodiment of the present invention is described.

With reference to Fig. 1, sphygmomanometer 1 has body 10 and can be wound on the cuff 20 on determined person's the wrist.Body 10 is installed on the cuff 20.For example dispose on the surface of body 10: display part 40, it is made up of liquid crystal etc.; Operating portion 41, it is used for receiving the indication from user's (representational is determined person).Operating portion 41 for example comprises a plurality of switches.

(about hardware configuration)

Utilize Fig. 2, the hardware configuration of the sphygmomanometer 1 of embodiment of the present invention is described.

With reference to Fig. 2, the cuff 20 of sphygmomanometer 1 comprises air bag 21.Air bag 21 is connected with air system 30 via air hose 31.

Body 10 is except comprising above-mentioned display part 40 and the operating portion 41, also comprising: air system 30; CPU (Central Processing Unit: CPU) 100, it is used for each one of centralized control, and carries out various calculation process; Storage part 42, it is used to store program and the various data that make the action that CPU100 puts rules into practice; Nonvolatile memory (for example flash memory) 43, it is used for the pressure value that storing measurement goes out; Power supply 44, it is used for CPU100 is supplied power; Timing portion 45, it carries out the timing action; Data input and output portion 46, it is used for receiving from the outside input of data; Buzzer 62, it is used to the sound etc. that gives a warning.

Operating portion 41 has: mains switch 41A, the input signal that it is used for accepting connection (ON) or closes the indication of (OFF) power supply; Measure switch 41B, it is used to accept the indication that begins to measure; Shutdown switch 41C, it is used to accept the indication that stops to measure; Storage switch 41D, it is used for accepting the indication of playback record in the information such as blood pressure of flash memory 43.In addition, operating portion 41 can also have ID switch (not shown), and this ID switch is operated in order to import ID (Identification: the identify) information that is used to discern mensuration person.Thus, can and read the survey regular data to each determined person's record.

Air system 30 comprises: pressure sensor 32, and it is used to detect the pressure (cuff pressure) in the air bag 21; Pump 51, its in order cuff to be compressed into row pressurization to air bag 21 air supplies; Valve 52, it is in order to discharge the air of air bag 21 or enclose and to open and close.

With above-mentioned air system 30 explicitly, body 10 also comprises amplifier 33, voltage/frequency change-over circuit (oscillating circuit) 34, pump drive circuit 53 and valve-driving circuit 54.

In this example, as an example of pressure sensor 32, be the pressure sensor of piezoresistance formula.The output voltage of 33 pairs of pressure sensors 32 of amplifier amplifies, and exports voltage/frequency change-over circuit 34 to.Voltage/frequency change-over circuit 34 will export CPU100 to via amplifier 33 in response to the signal of the frequency of oscillation of the output voltage of pressure sensor 32.State for behind 34 of the voltage/frequency change-over circuits.In addition; Output voltage of signals level difference (amplitude) from pressure sensor 32 is less; Therefore be provided with amplifier 33 in order to amplify this voltage level difference; But under the situation big, there is no need to be provided with especially this amplifier 33, can adopt and pressure sensor 32 direct-connected structures from the output voltage of signals level difference (amplitude) of pressure sensor 32.

CPU100 will convert pressure to from the frequency of oscillation that voltage/frequency change-over circuit 34 draws, and detect this pressure.The driving that pump drive circuit 53 comes control pump 51 based on the control signal of accepting from CPU100.Valve-driving circuit 54 carries out the open and close controlling of valve 52 based on the control signal of accepting from CPU100.

Be configured for adjustment sleeve adjusting mechanism 50 with pressure by pump 51, valve 52, pump drive circuit 53 and valve-driving circuit 54.In addition, be used for adjustment sleeve device with pressure, be not limited to these devices.

Data input and output portion 46 for example is used for carrying out reading or writing of program or data with detachable storage medium 132.In addition, data input and output portion 46 also can carry out the transmitting-receiving of program or data via the computer of communication line and not shown outside.

In addition; As shown in Figure 1; The sphygmomanometer 1 of this execution mode is that body 10 is installed in the mode on the cuff 20, but also can be as the mode that adopts in the last arm-type sphygmomanometer, connecting the mode of body 10 and cuff 20 by air hose (air hose 31 in Fig. 2).

In addition, adopted cuff 20 to comprise the mode of air bag 21, but the fluid that supplies in the cuff 20 being not limited to air, also can be for example liquid, gelinite.Perhaps, being not limited to fluid, also can be the uniform particulate of microballon etc.

In addition, in this execution mode, the location of regulation is a wrist, but is not as what limit, also can be other positions such as upper arm.

Utilize Fig. 3, the pressure sensor 32 of the piezoresistance formula of embodiment of the present invention is described.

With reference to Fig. 3, pressure sensor 32 is included in supply voltage Vd and fixed voltage is the resistive element Rp1～Rp4 that is connected in parallel between the earthed voltage GND.And the connected node between resistive element Rp1 and Rp2 is connected with lead-out terminal (+) side.In addition, the connected node between resistive element Rp3 and Rp4 is connected with lead-out terminal (-) side.In the pressure sensor of this piezoresistance formula, the resistance value of each resistive element changes according to pressure, follows in this, produces potential difference at lead-out terminal.Pressure sensor 32 will export voltage/frequency change-over circuit 34 to via amplifier 33 at the voltage signal that this lead-out terminal produces.

At first, existing RC oscillating circuit is described.

Utilize Fig. 4, existing RC oscillating circuit is described.

With reference to (a) part of Fig. 4, existing RC oscillating circuit comprises resistive element 12,13, NOR circuit (NOR circuit) 11A～11C and capacitor 14.

Resistive element 13 be located at node NA and node NB between.Resistive element 12 is located between input node one side of node NA and NOR circuit 11A.

An electrode of capacitor 14 is connected with node NA, and another electrode then is connected with node NC.Input node one side of NOR circuit 11A is connected with node NA via resistive element 12; Another input node one side is that earthed voltage GND is connected with fixed voltage then, and exports different NOR (XNOR) logic operation result input node one side of NOR circuit 11B to.

Input node one side of NOR circuit 11B is connected with the output node of NOR circuit 11A; Another input node one side of NOR circuit 11B is that earthed voltage GND is connected with fixed voltage then, and different NOR logic operation result is sent to the node NC of NOR circuit 11C.

Input node one side of NOR circuit 11C is connected with node NC, and another input node one side is that earthed voltage GND is connected with fixed voltage then, and different NOR logic operation result is sent to output node NB.

In addition, another input node of NOR circuit 11A, 11B, 11C is connected with earthed voltage GND.Therefore, this NOR circuit 11A, 11B, 11C are respectively as the phase inverter of output after the input signal counter-rotating is brought into play function.

Action to this RC oscillating circuit describes.

In the RC oscillating circuit, set frequency of oscillation according to special time, this special time is meant according to the time constant circuit that is made up of resistive element 13 and capacitor 14 and reaches the time till the threshold value of NOR circuit 11A.

Particularly, when the input node of NOR circuit 11A was set to " L " level (low level, the down together) output of NOR circuit 11A afterwards becoming " H " level (high level, down together), node NB also was set to " H " level via NOR circuit 11B, 11C.

And capacitor 14 is recharged and the voltage level of node NA when becoming " H " level, and the input node of NOR circuit 11A also becomes " H " level, thereby the output level of NOR circuit 11A changes.Follow in this, the output level of NOR circuit 11A is set to " L " level from " H " level, thereby node NB also is set to " L " level via NOR circuit 11B, 11C.

And when being accumulated in charge discharge and the voltage level of node NA in the capacitor 14 then and becoming " L " level, the input node of NOR circuit 11A also becomes " L " level, so the output level of NOR circuit 11A becomes " H " level from " L " level.And node NB also is set to " H " level via NOR circuit 11B, 11C.

Through should charging moving and discharging action repeatedly, alternating voltage output " L " level of node NB carries out oscillation action with " H " level.

Utilize Fig. 5, the voltage level of each node of existing RC oscillating circuit is described.

With reference to Fig. 5, the voltage waveform of node NA shown here, NB, NC.

Here, to describing during charging action and the discharging action.

Fig. 4 (b) part is the figure that is used to explain the charging action of the general time constant circuit that is made up of resistance value R and electrostatic capacitance C.

That is, resistance value R is equivalent to the resistance components of (a) resistive element 13 partly of Fig. 4, and electrostatic capacitance C then is equivalent to the capacitive component of (a) capacitor 14 partly of Fig. 4.

Voltage Vo with following this time constant circuit of formulate:

$\frac{\mathrm{Vi}-\mathrm{Vo}}{R}=C\frac{\mathrm{dVo}}{\mathrm{dt}}$

$\frac{1}{\mathrm{RC}}\&Integral;\mathrm{dt}=\&Integral;\frac{1}{\mathrm{Vi}-\mathrm{Vo}}\mathrm{dVo}$

$\frac{t}{\mathrm{RC}}+A=-\mathrm{Log}(\mathrm{Vi}-\mathrm{Vo})$ A: integral constant

$\mathrm{Vi}-\mathrm{Vo}=e^{-\frac{t}{\mathrm{RC}}+A}$

$\mathrm{Vo}=\mathrm{Vi}-{\mathrm{Be}}^{-\frac{t}{\mathrm{RC}}}\&CenterDot;\&CenterDot;\&CenterDot;\left(1\right)$

The initial condition that is used to calculate the integration constant A is when time t=0, under the situation of voltage Vo=0, with following formulate voltage Vo:

0＝Vi-B

B＝Vi

∴ $\mathrm{Vo}=\mathrm{Vi}-{\mathrm{Vie}}^{-\frac{t}{\mathrm{RC}}}$

$=\mathrm{Vi}(1-e^{-\frac{t}{\mathrm{RC}}})\&CenterDot;\&CenterDot;\&CenterDot;\left(2\right)$

The initial condition of moving in the charging of the RC oscillating circuit shown in Fig. 4 (a) part on the other hand, is following: begin the charging action after voltage has just reached Vth through discharging action.That is, when time t=0, the voltage Vo of node Na becomes Vth-Vd.

Therefore, if with initial condition substitution to formula (1), then become following formula:

Vth-Vd＝Vd-B(Vi＝Vd)

B＝2Vd-Vth

$\mathrm{Vo}=\mathrm{Vd}-(2\mathrm{Vd}-\mathrm{Vth})e^{-\frac{t}{\mathrm{RC}}}\&CenterDot;\&CenterDot;\&CenterDot;\left(3\right)$

If this formula is found the solution t, then become following formula:

$(2\mathrm{Vd}-\mathrm{Vth})e^{-\frac{t}{\mathrm{RC}}}=\mathrm{Vd}-\mathrm{Vo}$

$e^{-\frac{t}{\mathrm{RC}}}=\frac{\mathrm{Vd}-\mathrm{Vo}}{2\mathrm{Vd}-\mathrm{Vth}}$

$t=-\mathrm{RC}\log \left(\frac{\mathrm{Vd}-\mathrm{Vo}}{2\mathrm{Vd}-\mathrm{Vth}}\right)\&CenterDot;\&CenterDot;\&CenterDot;\left(4\right)$

This voltage Vo is sent to the input node of NOR circuit 11A, and when reaching the threshold value Vth of NOR circuit 11A, the output level of NOR circuit 11A changes and is set to " L " level.That is the time that, reaches the threshold value Vth of NOR (or non-) door is the time that becomes Vo=Vth.In addition, because the threshold value Vth of NOR door generally is 1/2 of supply voltage Vd, therefore as if substitution to top formula, then by following formulate:

$\mathrm{Vo}=\mathrm{Vd}-(2\mathrm{Vd}-\frac{1}{2}\mathrm{Vd})e^{-\frac{t}{\mathrm{RC}}}$

$=\mathrm{Vd}-\frac{3}{2}\mathrm{Vd}{e}^{-\frac{t}{\mathrm{RC}}}$

$=\mathrm{Vd}-(1-\frac{3}{2}{e}^{-\frac{t}{\mathrm{RC}}})\&CenterDot;\&CenterDot;\&CenterDot;\left(5\right)$

And available following formulate is carried out the required time tc of this above-mentioned charging action:

$t=-\mathrm{RC}\log \left(\frac{\mathrm{Vd}-\frac{1}{2}\mathrm{Vd}}{2\mathrm{Vd}-\frac{1}{2}\mathrm{Vd}}\right)$

$=-\mathrm{<figure-callout\; id="1"\; label="RC\; log"\; filenames="HPA00001424194100011.png"\; state="\{\{state\}\}">RC</figure-callout>}\log \frac{\frac{1}{2}}{\frac{3}{2}}\mathrm{Vd}$

$\mathrm{tc}=-\mathrm{<figure-callout\; id="1"\; label="RC\; log"\; filenames="HPA00001424194100011.png"\; state="\{\{state\}\}">RC</figure-callout>}\log \frac{1}{3}\mathrm{Vd}\&CenterDot;\&CenterDot;\&CenterDot;\left(6\right)$

Then, discharging action is considered.

Fig. 4 (c) part is the figure that is used to explain the discharging action of the general time constant circuit that is made up of resistance value R and electrostatic capacitance C.

That is, resistance value R is equivalent to the resistance components of (a) resistive element 13 partly of Fig. 4, and electrostatic capacitance C then is equivalent to the capacitive component of (a) capacitor 14 partly of Fig. 4.

Voltage Vo with following this time constant circuit of formulate:

$C\frac{d(\mathrm{Vi}-\mathrm{Vo})}{\mathrm{dt}}=\frac{\mathrm{Vo}}{R}$

$-\frac{\mathrm{dVo}}{\mathrm{dt}}=\frac{\mathrm{Vo}}{\mathrm{RC}}$

$\&Integral;\frac{1}{\mathrm{Vo}}\mathrm{dVo}=-\frac{1}{\mathrm{RC}}\&Integral;\mathrm{dt}$

$\log \mathrm{Vo}=-\frac{t}{\mathrm{RC}}+A$

$\mathrm{Vo}={\mathrm{Be}}^{-\frac{t}{\mathrm{RC}}}\&CenterDot;\&CenterDot;\&CenterDot;\left(7\right)$

Initial condition at the discharging action of the RC oscillating circuit shown in Fig. 4 (a) part is following: voltage begins discharging action after just having reached Vth through the charging action.That is, when time t=0, the voltage Vo of node NA becomes Vth+Vd.

Therefore, if with initial condition substitution to formula (7), then become following formula:

Vth+Vd＝B

∴ $\mathrm{Vo}=(\mathrm{Vth}+\mathrm{Vd})e^{-\frac{t}{\mathrm{RC}}}\&CenterDot;\&CenterDot;\&CenterDot;\left(8\right)$

If this formula is found the solution t, then become following formula:

$t=-\mathrm{RC}\log \left(\frac{\mathrm{Vo}}{\mathrm{Vth}+\mathrm{Vd}}\right)\&CenterDot;\&CenterDot;\&CenterDot;\left(9\right)$

The time that reaches the threshold value Vth of NOR door is the time that becomes Vo=Vth.In addition, because the threshold value Vth of NOR door generally is 1/2 of supply voltage Vd, therefore as if substitution to top formula, then by following formulate:

$\mathrm{Vo}=\frac{3}{2}\mathrm{Vd}{e}^{-\frac{t}{\mathrm{RC}}}\&CenterDot;\&CenterDot;\&CenterDot;\left(10\right)$

And available following formulate is carried out the required time td of this above-mentioned discharging action:

$\mathrm{td}=-\mathrm{<figure-callout\; id="1"\; label="RC\; log"\; filenames="HPA00001424194100011.png"\; state="\{\{state\}\}">RC</figure-callout>}\log \frac{1}{3}\mathrm{Vd}\&CenterDot;\&CenterDot;\&CenterDot;\left(11\right)$

Therefore, in the RC oscillating circuit shown in Fig. 4 (a) part,, therefore can access the impulse waveform of occupation efficiency (duty cycle) 50% owing to have the relation of time tc=td.

As stated, constituted for 1 cycle by the total ascent time of carrying out the required time td of required time tc of charging action and execution discharging action.

Therefore, as knowing,, frequency of oscillation is changed through making variations such as resistance components or capacitive component from top formula (6), (11).

In existing static capacity type sensor device, adopted and utilized this RC oscillating circuit to make capacitance variation, thus the mode that frequency of oscillation is changed.

Utilize Fig. 6, the voltage/frequency change-over circuit 34 of embodiment of the present invention is described.

With reference to Fig. 6, the voltage/frequency change-over circuit 34 of embodiment of the present invention comprises resistive element 12,13,16, NOR circuit 11A～11C, capacitor 14 and switch element 15.

Resistive element 16 is located between input terminal and the node N0.In addition, switch element 15 is located at node N0 and fixed voltage is between the earthed voltage GND, and according to the voltage level of node NC and conducting.In addition, resistive element 13 is located between node N0 and the node NA.Resistive element 12 is located between input node one side of node NA and NOR circuit 11A.

An electrode of capacitor 14 is connected with node NA, and another electrode then is connected with node NC.Input node one side of NOR circuit 11A is connected with node NA via resistive element 12, and opposite side is that earthed voltage GND is connected with fixed voltage then, and exports different NOR logic operation result input node one side of NOR circuit 11B to.

Input node one side of NOR circuit 11B is connected with the output node of NOR circuit 11A; Another input node one side of NOR circuit 11B is that earthed voltage GND is connected with fixed voltage then, and different NOR operation result is sent to the node NC of NOR circuit 11C.

Input node one side of NOR circuit 11C is connected with node NC, and opposite side is that earthed voltage GND is connected with fixed voltage then, and different NOR operation result is sent to output node NB.

In this example, also with the RC oscillating circuit likewise, set frequency of oscillation according to special time, this special time is meant according to the time constant circuit that is made up of resistive element 13,16 and capacitor 14 and reaches the time till the threshold value of NOR circuit 11A.

Particularly, when the input node of NOR circuit 11A was " L " level, this output signal was set to " H " level.Follow in this, the output signal of NOR circuit 11B is set to " L " level, and the output signal of NOR circuit 11C is set to " H " level.

Because the voltage level of node NC is " L " level; And; Because an electrode of capacitor 14 is connected with input terminal via resistive element 13,16; Therefore, according to the charging action of the time constant circuit that is made up of resistive element 13,16 and capacitor 14, the voltage of node NA can be used following formulate.That is, as stated, the initial condition that the charging of RC oscillating circuit is moved inputs to formula (1).

Initial condition is when time t=0, and the voltage Vo of node Na becomes Vth-Vd.

$\mathrm{Vo}=\mathrm{Vi}-{\mathrm{Be}}^{-\frac{t}{\mathrm{RC}}}\&CenterDot;\&CenterDot;\&CenterDot;\left(1\right)$

During t=0, Vo=Vth-Vd

∴Vth-Vd＝Vi-B

B＝Vi+Vd-Vth

$\mathrm{Vo}=\mathrm{Vi}-(\mathrm{Vi}+\mathrm{Vd}-\mathrm{Vth})e^{-\frac{t}{\mathrm{RC}}}\&CenterDot;\&CenterDot;\&CenterDot;\left(12\right)$

If this formula is found the solution t, then become following formula:

$t=-\mathrm{RC}\log \left(\frac{\mathrm{Vi}-\mathrm{Vo}}{\mathrm{Vi}+\mathrm{Vd}-\mathrm{Vth}}\right)\&CenterDot;\&CenterDot;\&CenterDot;\left(13\right)$

The time that reaches the threshold value Vth of NOR door is the time that becomes Vo=Vth.In addition, because the threshold value Vth of NOR door generally is 1/2 of supply voltage Vd, therefore as if substitution to top formula, then by following formulate:

$\mathrm{Vo}=\mathrm{Vi}-(\mathrm{Vi}+\frac{1}{2}\mathrm{Vd})e^{-\frac{t}{\mathrm{RC}}}\&CenterDot;\&CenterDot;\&CenterDot;\left(14\right)$

And, the required time te of this above-mentioned execution charging action of available following formulate:

$\mathrm{te}=-\mathrm{RC}\log \frac{\mathrm{Vi}-\frac{1}{2}\mathrm{Vd}}{\mathrm{Vi}+\frac{1}{2}\mathrm{Vd}}\&CenterDot;\&CenterDot;\&CenterDot;\left(15\right)$

And this charging voltage is sent to the input node of NOR circuit 11A, and when reaching the threshold value Vth of NOR circuit 11A, the output level of NOR circuit 11A changes and is set to " L " level.Follow in this, the output signal of NOR circuit 11B is set to " H " level from " L " level.And the output signal of NOR circuit 11C is set to " L " level from " H " level.

The output signal of NOR circuit 11B is set to " H " level, follows in this, and switch element 15 is according to the voltage level (" H " level) of node NC and conducting (connection).Thus, fixed voltage is that earthed voltage GND and node N0 are electrically connected.Follow in this, according to the discharging action of the time constant circuit that is made up of resistive element 13 and capacitor 14, the voltage of node NB can be used following formulate:

$\mathrm{td}=-\mathrm{RC}\log \left(\frac{1}{3}\mathrm{Vd}\right)\&CenterDot;\&CenterDot;\&CenterDot;\left(16\right)$

That is, same with above-mentioned formula (11).

This charging voltage is sent to the input node of NOR circuit 11A, and becomes the threshold value Vth of NOR circuit 11A when following, and the output level of NOR circuit 11A changes, and, is set to " H " level from " L " level that is.

And the output signal of NOR circuit 11B is set to " L " level from " H " level.In addition, the output signal of NOR circuit 11C is set to " H " level from " L " level.

The output signal of NOR circuit 11B is set to " L " level, follows in this, and switch element 15 becomes not conducting (disconnection) according to the voltage level (" L " level) of node NC.Thus, fixed voltage is that earthed voltage GND and node N0 electricity are separated.Follow in this, an electrode of capacitor 14 is connected with input terminal via resistive element 13,16, thereby carries out above-mentioned charging action.

That is, through above-mentioned charging action and discharging action, the output signal of NOR circuit 11C is " L " level, " H " level, " L " level ... Oscillator signal.

In the voltage/frequency change-over circuit 34 of this execution mode, the capacitive component and the resistance components of capacitor 14 and resistive element 12,13,16 are fixed values, and the input voltage that input terminal received changes.As stated, the input voltage that input terminal received is the output voltage of being exported according to pressure by pressure sensor.

Utilize Fig. 7, the voltage level of each node of the voltage/frequency change-over circuit 34 of embodiment of the present invention is described.

With reference to Fig. 7, the voltage level of node NA shown here and node NC.

In the structure of this execution mode, that is, in the structure that the input voltage that input terminal received changes, shown in formula (15), the charging interval, te changed.In addition, owing to the capacitive component and the resistance components of capacitor 14 and resistive element 12,13,16 are fixed, so do not change discharge time.In addition, the resistance value R of formula (15) is equivalent to the aggregate value of resistance components of the resistive element 13,16 of Fig. 6.Electrostatic capacitance C is equivalent to the capacitive component of the capacitor 14 of Fig. 6.

Because the charging interval that reaches till the threshold value of NOR circuit 11A is depended on input voltage, thus the cycle of oscillator signal change, thereby frequency of oscillation is changed.

That is, the voltage/frequency change-over circuit 34 of this execution mode will export CPU100 in response to the signal of the frequency of oscillation of the output voltage of pressure sensor 32, and CPU100 converts frequency of oscillation pressure to and detects this pressure.

Therefore, can realize low-cost and high-precision voltage/frequency change-over circuit with easy mode.In addition, can realize utilizing the blood pressure measurement apparatus of this voltage/frequency change-over circuit.

In addition; In the structure of Fig. 6; To input node and a fixed voltage is that the structure of the NOR circuit that is connected of earthed voltage GND (" L " level) is illustrated; But also can adopt the structure of utilizing NAND circuit (NAND circuit), to replace utilizing the structure of NOR circuit through adopting input a node and the structure that supply voltage Vd (" H " level) is connected.

In addition; In the structure of Fig. 6; Structure to utilizing NOR circuit 11A～11C is illustrated, but the input node of each NOR circuit 11A～11C is that earthed voltage GND is connected with fixed voltage, so this NOR circuit is brought into play function as the phase inverter that makes the logical level of input signals counter-rotating.Therefore, also can adopt the structure of replacing NOR circuit 11A～11C with phase inverter.Through this structure, the structural elements number of packages that can reduce circuit diminishes the layout (layout) of circuit.

(variation of execution mode)

Utilize Fig. 8, the voltage/frequency change-over circuit 34# of the variation of embodiment of the present invention is described.

With reference to Fig. 8; With compare at voltage/frequency change-over circuit 34 illustrated in fig. 6; The difference of the voltage/frequency change-over circuit 34# of the variation of embodiment of the present invention is, also is provided with NOR circuit 11D, resistive element 17,20,21, switch element 18 and electric capacity 19.

Particularly, resistive element 17 is located between input terminal and the node N1.In addition, switch element 18 is located between node N1 and the fixed voltage, and becomes conducting/not conducting according to the voltage level of node NB.Resistive element 20 is located between node NE and the node N1.An electrode of electric capacity 19 is connected with node NE, and another electrode then is connected with node NB.The input node of NOR circuit 11D is connected with node NB, and another input node then is connected with fixed voltage, and the NOR logic operation result is sent to node ND.A Lead-through terminal of resistive element 21 is connected with node NE, and another Lead-through terminal then is connected with the input node of NOR circuit 11B.

NOR circuit 11B accepts the output signal of NOR circuit 11A and from the input via the signal of the node NE of resistive element 21, and different NOR logic operation result is sent to node NC.

Structure for above-mentioned execution mode; To the mode of adjusting during " H " level of oscillator signal being illustrated according to the input voltage adjustment charging interval; But in the structure of the variation of this execution mode, to so that the mode of adjusting during " L " level of oscillator signal described.

Particularly, when the input node of NOR circuit 11A was " L " level, as stated, the output signal of NOR circuit 11C was set to " H " level.Follow in this, the output signal of NOR circuit 11B is set to " L " level, and the output signal of NOR circuit 11C then is set to " H " level.In addition, the output signal of NOR circuit 11D is set to " L " level.

In this case, because node NC is " L " level, so switch element 15 not conductings.On the other hand, because node NB is " H " level, so switch element 18 conductings.Therefore, fixed voltage is that earthed voltage GND combines with node N1 electricity.That is the input node that, receives via the resistive element of NOR circuit 11B 20,21 is set to " L " level.Thereby,, therefore bring into play function as phase inverter because the input node of NOR circuit 11B is " L " level.

Then, because the voltage level of node NC is " L " level, and because an electrode of capacitor 14 is connected with input terminal via resistive element 13,16 as above-mentioned, therefore carrying out charges moves.And through the charging action, the voltage of node NA is sent to the input node of NOR circuit 11A, and when reaching the threshold value Vth of NOR circuit 11A, the output level of NOR circuit 11A changes and is set to " L " level.Follow in this, the output signal of NOR circuit 11B is set to " H " level from " L " level.And the output signal of NOR circuit 11C is set to " L " level from " H " level.And the output signal of NOR circuit 11D is set to " H " level from " L " level.

The output signal of NOR circuit 11B is set to " H " level, follows in this, and switch element 15 is according to the voltage level (" H " level) of node NC and conducting (connection).Thus, fixed voltage is that earthed voltage GND is electrically connected with node N0.Follow in this, carry out discharging action.At this moment, because the output signal of NOR circuit 11C is set to " L " level from " H " level, thereby switch element 18 becomes not conducting (disconnection).On the other hand, because the output signal of NOR circuit 11A is " L " level, and because the input node of NOR circuit 11B is " L " level, so this NOR circuit 11B brings into play function as phase inverter.

Then, because the output signal of NOR circuit 11C is " L " level, and the voltage level of node NB is " L " level, and because an electrode of electric capacity 19 is connected with input terminal via resistive element 17,20, so this electric capacity 19 is carried out charging and moved.And through the charging action, the voltage of node NE is sent to the input node of NOR circuit 11B, and when reaching the threshold value Vth of NOR circuit 11B, the output level of NOR circuit 11B changes and is set to " L " level.Thus, switch element 15 becomes not conducting (disconnection).Therefore, fixed voltage is that earthed voltage GND and node N0 electricity are separated.Follow in this, an electrode of capacitor 14 is connected with input terminal via resistive element 13,16, so this capacitor 14 is carried out above-mentioned charging action.

In addition, the output level of NOR circuit 11B is set to " L " level, follows in this, and the output level of NOR circuit 11C is set to " H " level from " L " level.Therefore, because the output signal of NOR circuit 11C is " H " level, thereby switch element 18 conductings.Follow in this, node N1 is connected with earthed voltage GND.Follow in this, carry out discharging action.

That is, through above-mentioned charging action and discharging action, the output signal of NOR circuit 11D is " H " level, " L " level, " H " level, " L " level ... It is oscillator signal.

In addition; Resistance components and the capacitive component of the voltage/frequency change-over circuit 34# of this execution mode are set to; Make according to the time constant circuit that constitutes by resistive element 17,20 and electric capacity 19 and node NE reaches the charging interval of the threshold value Vth of NOR circuit 11B that beguine is short the discharge time that node NA becomes below the threshold value Vth of NOR circuit 11A according to the time constant circuit that is made up of resistive element 13 and capacitor 14.

In the voltage/frequency change-over circuit 34# of this execution mode, the capacitive component and the resistance components of capacitor 14,19 and resistive element 12,13,16,17,20,21 are fixed values, and the input voltage that input terminal received changes.As stated, the input voltage that input terminal received is the output voltage of being exported according to pressure by pressure sensor.

Utilize Fig. 9, the voltage level of each node of the voltage/frequency change-over circuit 34# of the variation of embodiment of the present invention is described.

With reference to (a) part of Fig. 9, the voltage level of node NA shown here and node NE.

In the structure of the variation of this execution mode, that is, in the structure that the input voltage that input terminal received changes, the charging interval tf of node NA and the charging interval tg of node NE change.In addition, owing to the capacitive component and the resistance components of capacitor 14,19 and resistive element 12,13,16,17,20,21 are fixed, so do not change discharge time.

Below, the charging interval of node NA and the charging interval of node NE are described.

At first, node NE is described.

Initial condition during as charging is when t=0, and Vo becomes 0-Vd.

Therefore, if the substitution initial condition, then the voltage of node NE is shown in following formula:

$\mathrm{Vo}=\mathrm{Vi}-{\mathrm{Be}}^{-\frac{t}{\mathrm{RC}}}$

-Vd＝Vi-B

B＝Vi+Vd

∴ $\mathrm{Vo}=\mathrm{Vi}-(\mathrm{Vi}+\mathrm{Vd})e^{-\frac{t}{\mathrm{RC}}}\&CenterDot;\&CenterDot;\&CenterDot;\left(17\right)$

If this formula is found the solution t, then become following formula:

$t=-\mathrm{RC}\log \frac{\mathrm{Vi}-\mathrm{Vo}}{\mathrm{Vi}+\mathrm{Vd}}\&CenterDot;\&CenterDot;\&CenterDot;\left(18\right)$

The time that reaches the threshold value Vth of NOR door is the time that becomes Vo=Vth.

Therefore, the required time tg of this above-mentioned execution charging action, available following formulate:

$\mathrm{tg}=-\mathrm{RC}\log \frac{\mathrm{Vi}-\mathrm{Vth}}{\mathrm{Vi}+\mathrm{Vd}}\&CenterDot;\&CenterDot;\&CenterDot;\left(19\right)$

In addition, the resistance value R of formula (19) is equivalent to the aggregate value of resistance components of the resistive element 17,20 of Fig. 8.Electrostatic capacitance C is equivalent to the capacitive component of the electric capacity 19 of Fig. 8.

Then, node NA is considered.

At first, the initial condition the during discharge of node NA becomes Vo=Vth+Vd when t=0.

Therefore, for node NA, like above-mentioned explanation, the top node NA of formula (8) when obtaining discharging capable of using.

On the other hand; As stated; Resistance components and the capacitive component of the voltage/frequency change-over circuit 34# of this execution mode are set to; Make that node NE reaches the charging interval of the threshold value Vth of NOR circuit 11B through the time constant circuit that is made up of resistive element 17,20 and electric capacity 19, shorter than the discharge time that the node NA through the time constant circuit that is made up of resistive element 13 and capacitor 14 becomes below the threshold value Vth of NOR circuit 11A.

Therefore, as shown in Figure 9, when node NE reached the threshold value Vth of NOR circuit 11B, node NA was set to the voltage than the high assigned voltage of threshold value Vth.

Therefore, at first, the voltage when obtaining node NE and reaching the threshold value Vth of NOR circuit 11B.

Particularly, the voltage of node NE is become time tg substitution to the top formula (8) of Vth:

$\mathrm{Vo}=(\mathrm{Vth}+\mathrm{Vd})e^{-\frac{t}{\mathrm{RC}}\&times;(-\mathrm{RC}\log \frac{\mathrm{Vi}-\mathrm{Vth}}{\mathrm{Vi}+\mathrm{Vd}})}$

$=(\mathrm{Vth}+\mathrm{Vd})\&CenterDot;e^{\log \frac{\mathrm{Vi}-\mathrm{Vth}}{\mathrm{Vi}+\mathrm{Vd}}}$

$\frac{\mathrm{Vo}}{\mathrm{Vth}+\mathrm{Vd}}=e^{\log \frac{\mathrm{Vi}-\mathrm{Vth}}{\mathrm{Vi}+\mathrm{Vd}}}$

$\log \frac{\mathrm{Vo}}{\mathrm{Vth}+\mathrm{Vd}}=\log \frac{\mathrm{Vi}-\mathrm{Vth}}{\mathrm{Vi}+\mathrm{Vd}}$

∴ $\frac{\mathrm{Vo}}{\mathrm{Vth}+\mathrm{Vd}}=\frac{\mathrm{Vi}-\mathrm{Vth}}{\mathrm{Vi}+\mathrm{Vd}}$

$\mathrm{Vo}=\frac{(\mathrm{Vth}+\mathrm{Vd})(\mathrm{Vi}-\mathrm{Vth})}{\mathrm{Vi}+\mathrm{Vd}}=K\&CenterDot;\&CenterDot;\&CenterDot;\left(20\right)$

This voltage is the voltage of the node NA of the voltage of node NE when becoming Vth.

Because the initial condition the during charging of node NA action is when t=0, Vo=K-Vd, thereby during with this initial condition substitution to formula (1), the voltage of node NA is shown in following formula:

k-Vd＝Vi-B

B＝Vi+Vd-K

$\mathrm{Vo}=\mathrm{Vi}-(\mathrm{Vi}+\mathrm{Vd}-K)e^{-\frac{t}{\mathrm{RC}}}\&CenterDot;\&CenterDot;\&CenterDot;\left(21\right)$

If this formula is found the solution t, the required time tf of above-mentioned execution charging action then becomes following formula:

$\mathrm{tf}=-\mathrm{RC}\log \frac{\mathrm{Vi}-\mathrm{Vth}}{\mathrm{Vi}+\mathrm{Vd}-k}$

$=-\mathrm{RC}\log \frac{\mathrm{Vi}-\mathrm{Vth}}{\mathrm{Vi}+\mathrm{Vd}-\frac{(\mathrm{Vth}+\mathrm{Vd})(\mathrm{Vi}-\mathrm{Vth})}{\mathrm{Vi}+\mathrm{Vd}}}\&CenterDot;\&CenterDot;\&CenterDot;\left(22\right)$

In addition, the resistance value R of formula (22) is equivalent to the aggregate value of resistance components of the resistive element 13,16 of Fig. 8.Electrostatic capacitance C is equivalent to the capacitive component of the capacitor 14 of Fig. 8.

Therefore since the charging interval that reaches till the threshold value of NOR circuit 11A and NOR circuit 11B depend on input voltage, thereby the cycle of oscillator signal change, thereby frequency of oscillation is changed.

That is, the voltage/frequency change-over circuit 34# of this execution mode will export CPU100 in response to the signal of the frequency of oscillation of the output voltage of pressure sensor 32, and CPU100 converts frequency of oscillation pressure to and detects this pressure.

Therefore, can realize low-cost and high-precision voltage/frequency change-over circuit with easy mode.In addition, can realize utilizing the blood pressure measurement apparatus of this voltage/frequency change-over circuit.

In addition; In the structure of the variation of this execution mode; Utilization is adjusted the charging interval by the time constant circuit that resistive element 13,16 and capacitor 14 constitute according to input voltage, thus " H " level of the node NB of furnishing oscillator signal during, simultaneously; Utilization is adjusted the charging interval by the time constant circuit that resistive element 17,20 and electric capacity 19 constitute according to input voltage, adjust thus oscillator signal node NB " L " level during.

Thus, the oscillator signal of the NOR circuit 11D of the reverse signal of adjustment output node NB is a frequency of oscillation.

In addition; In the structure of Fig. 8; To input node and a fixed voltage is that the structure of the NOR circuit 11A that is connected of earthed voltage GND (" L " level), 11C, 11D is illustrated; But also can adopt the structure of utilizing the NAND circuit, to replace utilizing the structure of NOR circuit through adopting input a node and the structure that supply voltage Vd (" H " level) is connected.

In addition, in the structure of Fig. 8, also can adopt so that the structure that the phase inverter of logical level of input signals counter-rotating is replaced each NOR circuit respectively, to replace utilizing the structure of NOR circuit 11A, 11C, 11D.Through this structure, the structural elements number of packages that can reduce circuit diminishes the layout of circuit.

According to the structure of the variation of this execution mode, adjust according to input voltage oscillator signal " H " level during and " L " level during, therefore can obtain dynamic range widely, and can realize more high-precision voltage/frequency change-over circuit.In addition, can realize utilizing the blood pressure measurement apparatus of this voltage/frequency change-over circuit.

Will be understood that execution mode of the present disclosure is in the illustrations of whole points and unrestricted.Scope of the present invention also can't help above-mentioned explanation and is represented, but is represented by claims, is intended to be included in and the meaning that claims are impartial and the whole changes in the scope.

The explanation of Reference numeral

1 electrosphygmomanometer

10 bodies

20 cufves

21 air bags

30 air systems

31 air hoses

32 pressure sensors

33 amplifiers

34,34# voltage/frequency change-over circuit

40 display parts

41 operating portions

The 41A mains switch

41B measures switch

The 41C shutdown switch

The 41D storage switch

42 storage parts

43 flash memories

44 power supplys

45 timing portions

46 data input and output portions

50 adjusting mechanisms

51 pumps

52 valves

53 pump drive circuits

54 valve-driving circuits

62 buzzers

100?CPU

132 storage mediums

Claims (5)

1. a voltage/frequency change-over circuit is characterized in that,

This voltage/frequency change-over circuit has the RC oscillating circuit (34) that comprises capacitive component and resistance components,

Said RC oscillating circuit comprises:

Input terminal, it is used to receive input voltage,

First resistive element (13,16), it is connected between said input terminal and first internal node (NA),

First capacitor (14), one electrode is connected with said first internal node, and its another electrode is connected with second internal node (NC),

Second resistive element (12), itself and said first capacitor are in parallel, and an one of which Lead-through terminal is connected with said first internal node,

First logical circuit (11A, 11B), it is connected with another Lead-through terminal of said second resistive element, and is connected between said first internal node and said second internal node via said second resistive element,

Second logical circuit (11C), it is connected with said second internal node, is used to export the oscillator signal in response to the output signal of said first logical circuit,

First switch element (15), it is electrically connected said first internal node and the fixed voltage that are connected with a said electrode, so that said first capacitor carries out charge/discharge according to the voltage level of said second internal node.

2. according to the voltage/frequency change-over circuit of claim 1 record, it is characterized in that said input voltage is equivalent to the output voltage of piezoresistance formula transducer.

3. according to the voltage/frequency change-over circuit of claim 1 record, it is characterized in that,

Said first switch element is threshold value conducting when above at the voltage level of said second internal node, so that first internal node and the fixed voltage that are connected with a said electrode be electrically connected, thereby said first capacitor is discharged;

Said first switch element is in the not conducting during less than threshold value of the voltage level of said second internal node, so that first internal node that is connected with a said electrode is connected with said input voltage, thereby said first capacitor charged.

4. according to the voltage/frequency change-over circuit of claim 1 record, it is characterized in that,

Comprise:

The 3rd resistive element (17,20), it is connected between said input terminal and the 3rd internal node (NE),

Second capacitor (19), one electrode is connected with said the 3rd internal node, and another electrode is connected with the 4th internal node (NB),

The 4th resistive element (21), itself and said second capacitor are in parallel, and an one of which Lead-through terminal is connected with said the 3rd internal node;

Said first logical circuit has:

First phase inverter (11A), it is connected with another Lead-through terminal of said second resistive element,

Exclusive-OR circuit (11B), its receive said first phase inverter lead-out terminal and said the 4th resistive element another Lead-through terminal input signal and export said second internal node to;

Said second logical circuit has:

Second phase inverter (11C), it is connected between said second internal node and said the 4th internal node,

The 3rd phase inverter (11D), it is connected with said the 4th internal node;

This voltage/frequency change-over circuit also comprises second switch element (18); This second switch element (18) is according to the voltage level of said the 4th internal node; Said the 3rd internal node and the fixed voltage that are connected with a said electrode are electrically connected, thereby said second capacitor is discharged.

5. a blood pressure measurement apparatus is characterized in that,

Have:

Cuff (20), it is used to be wound on the location of determined person's regulation,

Pressure sensing cell (32), it detects the pressure in the cuff;

Said pressure sensing cell comprises:

Piezoresistance formula transducer (Rp1～Rp4), its be used to produce with said cuff in the corresponding voltage of pressure,

RC oscillating circuit (34), it comprises capacitive component and resistance components;

Said RC oscillating circuit comprises:

Input terminal, it is used to receive input voltage,

First resistive element (13,16), it is connected between said input terminal and first internal node (NA),

First capacitor (14), one electrode is connected with said first internal node, and its another electrode is connected with second internal node,

Second resistive element (12), itself and said first capacitor are in parallel, and an one of which Lead-through terminal is connected with said first internal node,

First logical circuit (11A, 11B), it is connected with another Lead-through terminal of said second resistive element, and is connected between said first internal node and said second internal node via said second resistive element,

Second logical circuit (11C), it is connected with said second internal node, is used to export the oscillator signal in response to the output signal of said first logical circuit,

First switch element (15), it is electrically connected said first internal node and the fixed voltage that are connected with a said electrode, so that said first capacitor carries out charge/discharge according to the voltage level of said second internal node.

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